The generic class of materials covered by .alpha.-olefin/hindered vinylidene monomer substantially random interpolymers and including materials such as ethylene/vinyl aromatic monomer interpolymers are known in the art. For example, substantially random ethylene/styrene interpolymers, including pseudo-random interpolymers as described in EP 415815 A, offer a range of material structures and properties which makes them useful for varied applications, including the compatibilization of blends of polyethylene and polystyrene as described in U.S. Pat. No. 5,460,818. Random copolymers of aromatic vinyl monomer and an .alpha.-olefin having 4 to 12 carbon atoms are described in U.S. Pat. No. 5,244,996. Limited generic reference can be found to terpolymers of ethylene/styrene/.alpha.-olefin materials, but to date no evidence has been found which describes the effective incorporation of monomers into a copolymer, with examples in JP 07,278,230 limited to 2 mole percent or less incorporation of styrene in ethylene/.alpha.-olefin copolymers.
Although of utility in their own right, Industry is constantly seeking to further expand the applicability of these generic interpolymers, and especially those based on .alpha.-olefin/vinylidene aromatic monomers, such as ethylene/styrene interpolymers. Desired improved or superior performance characteristics to current state of the art materials can include, but are not limited to, an extended temperature range of application and low temperature performance, desirable mechanical properties and melt processability. The interpolymers of this invention provide an effective technology to address such needs.